Obstruction of male genital duct system is a common cause of infertility. Male infertility cases presenting with obstruction of the seminal tract may be primary or secondary to inflammatory events and/or surgery. Obstructive azoospermia may be due to obstruction at different levels (rete testis, epididymis, vas or ejaculatory duct). Epididymis is the most common site of single-site obstructions in the genital tract. Obstructive azoospermia is diagnosed by the absence of spermatogenic cells in the semen, presence of spermatozoa in seminiferous tubules of a normal sized testis and normal FSH in serum.The diagnosis of the site of the obstruction is either absent or limited due to limited available means for diagnosis. Vasography and transrectal ultrasound (TRUS) examination may help in the diagnosis of vasal and ejaculatory duct obstructions. Epididymal obstruction is difficult to be diagnosed by the present available diagnostic means and the decision to explore epididymis surgically is made only intraoperatively . High resolution ultrasonography is the best imaging modality for evaluation of the scrotal compartment and epididymis can routinely be identified on newer real time sonography.Our study tried to predict the presence or absence of sperms in the suspected obstructed epididymis through sonographic epididymal measurements thus helping the prior selection of patients either for reconstructive surgery or assisted reproductive techniques.Seventy males were included in this study; 30 with obstructive azoospermia and 20 with non obstructive azoospermia and 20 normal fertile men as a control group. Each patient under study was subjected to the history taking, complete clinical examination, semen analysis, high resolution scrotal ultrasound, serum F.S.H and testicular biopsy. Obstructive azoospermic patients were also subjected to transrectal ultrasound (TRUS) and epididymal sperm retrieval.Results showed that there were cut off levels of sonographic total epididymal volume (7 cc) and epididymal head volume (1.5 cc) that could differentiate between sperm containing epididymides and empty epididymides of patients with obstructive azoospermia. We tried to correlate between sonographic testicular and epididymal measurements in each group. In obstructive azoospermic patients we could predict epididymal length from testicular length through certain equation but correlation with the presence or absence of sperms in the epididymis was not established because epididymal length did not had a cut off level that could differentiate between presence or absence of sperms in the epididymis. In non obstructive cases we couldn't predict any of epididymal measurements from testicular measurements. In normal fertile men we could predict epididymal length from testicular length.We can conclude that the presence or absence of sperms in the epididymis of obstructive azoospermic patients can be predicted through calculating sonographic total epididymal volume mainly and to lesser extent the sonographic epididymal head volume of obstructive azoospermic patients prior to reconstructive surgery or intracytoplasmic sperm injection.